1. Field of the Invention
The present invention relates to a control module for controlling the actuation of hydraulically driven fuel injectors and intake/exhaust valves for an internal combustion engine.
2. Description of Related Art
Compression ignition internal combustion engines contain a plurality of reciprocating pistons located within combustion chambers of an engine block. Associated with each piston is a fuel injector that sprays a highly pressurized fuel into the combustion chamber. The fuel is mixed with air that is introduced into the chamber through an intake valve. After combustion the exhaust flows out of the chamber through an exhaust valve. The injection of fuel and movement of the intake and exhaust valves are typically controlled by mechanical cams. Cams are relatively inefficient and susceptible to wear. Additionally, the cams do not allow the engine to vary the timing of fuel injection, or the opening and closing of the intake/exhaust valves.
U.S. Pat. No. 5,255,641 issued to Schechter and assigned to Ford Motor Co. and U.S. Pat. No. 5,339,777 issued to Cannon and assigned to Caterpillar Inc. disclose hydraulically driven intake/exhaust valves that do not require cams to open and close the valves. The movement of the intake/exhaust valves is controlled by a solenoid actuated fluid valve(s). When the fluid valve(s) is in one position an hydraulic fluid flows into an enclosed stem portion of the intake/exhaust valve. The hydraulic fluid exerts a force on the stem which opens the valve. When the fluid valve(s) is switched to another position the intake/exhaust valve moves back to the original closed position. The fluid valve(s) is switched by an electronic controller. The controller can vary the timing of the intake/exhaust valves to optimize the performance of the engine.
U.S. Pat. No. 5,460,329 issued to Sturman discloses an hydraulically driven fuel injector. The Sturman injector contains a solenoid actuated fluid valve that is connected to an electronic controller. The valve and controller control the timing and amount of fuel injected into the combustion chamber of the engine. To date the camless intake/exhaust valves disclosed in Schechter and Cannon, and the hydraulically driven fuel injector disclosed in Sturman have always been provided as separate units which must be individually assembled to the engine block. Each unit has separate electrical wires that must be connected to the engine controller. Connecting a number of wires and separate actuating components increases the assembly cost of the engine. Additionally, because of manufacturing tolerances there may be variations in the lengths of the wires. A variation in the wire length may change the timing and amplitude of the driving signals transmitted to the solenoid actuated control valves. A change in the driving signals may degrade the performance of the engine. It would be desirable to provide a single electronic hydraulic module that controls camless hydraulically driven intake/exhaust valves and a fuel injector of a combustion chamber. It would also be desirable if the single module had a minimum number of external wires.
The solenoid actuated fluid valves for the intake/exhaust valves are typically connected to a single microprocessor which can vary the valve timing in response to variations in a number of input parameters such as fuel intake, hydraulic rail pressure, ambient temperature, etc. The microprocessor can vary the start time and the duration of the driving signal provided to the fluid valves to obtain a desired result. Because of variations in manufacturing tolerances, different valves may have different responses to the same driving pulse. For example, given the same driving pulse one intake valve may open for a shorter period of time than another intake valve in the same engine.
The Schechter patent discusses a process wherein each valve is calibrated to determine a correction value. The correction value is stored within the electronics of the engine and used to either shorten or lengthen the driving pulse provided to each valve so that the valves are all open for the same time duration. Although effective in compensating for variations in manufacturing tolerances, the Schechter technique does not compensate for variations that occur during the life of the engine. For example, one of the valves may stick and require more energy to move into an open position. It would be desirable to provide a module which can individually analyze the intake/exhaust valves and fuel injector to insure that the corresponding combustion chamber is operating at an optimum performance during the life of the engine.
The hydraulic fluid for hydraulically driven fuel injectors is typically provided by a pump and a series of fluid lines. The fluid system typically contains a spring biased pressure relief valve which opens to insure that the fluid pressure does not exceed a certain level. The pump performs work to overcome the spring of the relief valve during the by-pass mode of the system. It would be desirable to provide an hydraulic system for a camless engine, wherein the fluid pressure can be controlled without any additional components, or without requiring additional work by the pump to reduce the pressure within the system.
Some internal combustion engines contain a "turbocharge" assembly which varies the air flow into the combustion chambers. Some turbochargers contain complicated electronic devices to vary and control the air flow into the chamber. The electronic devices add to the cost and complexity of the engine. It would be desirable to provide a single control module that can control a fuel injector, an intake valve, an exhaust valve and a turbocharge unit.